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What could I do to a give a plane an emergency boost of power for takeoff?
For some reason the pilot has to take off in an emergency or is on a runway too short or maybe they just want more places they can land and takeoff. The single engine plane is already light on fuel and cargo. Could adding Nitrous oxide or richer fuel or something like an afterburner for a piston engine work?

You could strap a few rockets to the fuselage.

However you increase the engine's power, via forced induction or oxidizers or other "aftermarket" equipment, to use an automotive term, you risk overheating it exactly when it lacks the cooling airflow of cruise flight.

Rather than to modify the engine it may be better to add a jet engine or 2 on the wings.  Also, there are also STOL kits for planes, which can include canards just behind the nose prop.  It may also be possible to mount a more powerful engine (or even a turboprop).  But on the spot, it may be better to reduce weight as much as possible, and do a rolling takeoff from the taxiway.  If in doubt, consider the consequences of a crash, and what type of planning was done to get into that situation.

Adding nitrous oxide, or strapping on booster rockets, would take quite a bit of time, which means your "emergency" must have been planned well in advance. That means it's not an emergency: "a serious, unexpected, and often dangerous situation requiring immediate action."  If you just want to be able to use shorter runways, there are plenty of STCs for STOL mods for various airplanes.  Few if any of them involve engine modification. (Though sometimes a different, more powerful engine is installed.)

Besides some sort of Wile E. Coyote ACME style device there's nothing you can do if you're in some sort of remote location and need a boost. Lighten up as much as you can and take off into a strong wind.

There are some aircraft that can take off really, really short. About 25 feet for the take-off roll, and 27 for the landing in this case... The point is to pick the aircraft to suit the mission...

That really depends how safely you want to get off the ground.
If you are looking to get in and out of tight airfields using STC'ed parts you may want to consider a STOL kit which can modify the plane such that you can utilize a shorter runway.
There are some airframes that do have horsepower increase modifications available but that takes actual mechanic work and wont really be feasible in your "pinch" scenario.
There are a few aircraft that can be operated with JATO rockets and it looks like it was done at least once on an ercoupe during testing
You could add Nos but then again most pilots prefer their engine to run for the duration of the flight... You would also have to contend with the fact that adding NOS may very well require a direct port bore, which is no small job.
Afterburners don't really apply to internal combustion engines, at least not ones that generate meaningful thrust...

Most methods of increasing engine power would require major modifications to the engine which would require a Supplemental Type Certificate from the FAA. This would include the use of alternative fuels or fuel additives.
A better and much easier method to achieve your goals of shorter runway requirements is to reduce the aircraft weight. This can be achieved by carrying fewer passengers or less fuel. In certain extreme circumstances, you can also lighten the airframe itself by removing unused seats or even doors. But, it may make the aircraft unairworthy.


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How does fuel economy on Diamond DA62 change as passenger weight increases?
How many more gallons per hour is required to fly extra 1kg of weight on a Diamond DA62 aircraft or similar aircraft?

Have you looked for the Pilot Information Manual (PIM) for the plane?

You'd need the fuel consumption and cruise performance charts for the plane and extrapolate the number from the speed penalty you incur from an increase in weight from x to y. Normal cruise power is 75% of maximum. You might find that at a 75% power setting at a minimum weight, each extra kg costs you some fraction of a knot in cruise speed. Work out the increased power required to maintain that speed, and the fuel burn from that power increase, and there you are.

Related for jet aircraft: How much does it cost extra to fly with one additional passenger?

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What is that green dashed circle on ND?
I think this is a navigation display from a boeing aircraft

I searched around the internet for the meaning of the "green dashed circles" but got nothing.
Thanks in advance for your answers!

Welcome to Av.SE -- nice question!

When a point is entered into the FIX page in the FMC, the point's symbol (VOR or DME or waypoint or whatever) is displayed in green on the ND; if you enter a radial/distance then you get a circle around the point of the specified radius and a straight line on the given radial.  Alternatively, one can enter just the radius (as /20, instead of 180/20) and you get just the dashed circle.
In the picture in the OP, it looks like the destination airport has been entered in the fix page, with three distance-only entries, thus giving 3 concentric circles. The 087/267 degree radial displayed appears to be the course selected with the co-located VOR tuned in.
The following picture shows the FIX page with the I-AHI ILS DME transmitter entered, and a radial/distance of 090/10 entered:

(The 328/1.6 is the aircraft's current radial/distance from the fix.)
On the ND, it looks like this:

Note that the 090 radial from the fix is shown, but the reciprocal 270 radial is not. Contrast that with the BRK VOR (near the bottom of the display) which is tuned in the #1 NAV receiver with a 165 course dialed in - that radial is shown as both the 165 and the reciprocal 345 degree courses.
This has various uses; if I get a report of turbulence "50NM south of XYZ" (XYZ not being on my route) then I can put XYZ in the FIX page, and then below it enter 180/50 and I can then see the location of the turbulence report in relation to my (magenta line) course.  Alternatively, if I want to be at 10,000' and 250 knots at 36 NM from my destination, I can enter the destination (or even a runway) in the FIX page, and "/36" below it, and I'll get a 36 NM ring around the destination.  Then when I'm crossing that ring I can compare my actual altitude & airspeed and have a good idea if I have more or less energy than desired.
I'll also use the ring as a reminder of some action I want to take at a given point... if I know the ride will turn choppy in the vicinity of XYZ (which may or may not be on my route), I might put a 50NM ring around XYZ as a reminder that as we approach that point, I want to turn the seatbelt sign back on & call the flight attendants to take their seats.  I'll also mention that plan to the other pilot so that we're both on the same page as to how we plan to deal with the bad ride ahead.

Extremely helpful answer! Thank you very much!

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Can commercial aircraft be equipped with ECM and ECCM equipment?
I've came across an article recently about a commercial aircraft that was traveling from Madrid to Toronto and could not ascend to a higher altitude due to GPS Jamming.
With this apparent situation that just happened, can a commercial aircraft be equipped with ECM and ECCM equipment to prevent it from being a target of electronic warfare? Or this is strictly for military aircraft?

Do you happen to have a link to the article?

ECM or ECCM wouldn't "un-jam" your GPS receiver. Having the codes to access the encrypted GPS signals might help, depending on the nature of the jamming, but that's not at all certain.

Also, most GPS jamming is not targeted at a specific aircraft (though this is possible, with sufficiently sophisticated equipment), but usually affects everything within line-of-sight of the jammer. The idea that a particular commercial aircraft would be individually targeted for GPS jamming (or, more likely, spoofing) is a little far-fetched.

you seem to misunderstand what ECM and ECCM equipment does. It doesn't stop you being the target of jamming. It does the jamming itself.

Why would jamming GPS - which determines your lateral position - prevent the aircraft from climbing? Aircraft carry altimeters which are far more accurate than needed to know one's flight level. (I could see a case where you would be hesitant to descend without GPS coordinates, in case of terrain, but an ordinary airliners wouldn't get that close anyway.)

@Cadence  It wouldn't physically disable the aircraft from climbing, but if the higher airspace required ADSB, which in turn needs GPS input, then that could result in denied permission. If the OP would post a link to the article about this incident, that would be helpful.

a commercial aircraft that was traveling from Madrid to Toronto and could not ascend to a higher altitude due to GPS Jamming

Intentional jammers are easily localized and thrown to jail. It's very dubious a jammer was on the route Madrid-Toronto, mostly over the ocean.
In short
It's not possible to recover a jammed/spoofed GNSS signal. The reason is the original signal is not received, it is flooded by the jammer which signal is stronger than the satellite one at the reception point.

For a receiver, the satellite signal strength is quasi-constant, but the jammer signal, initially faint, has a strength multiplied by 4 each time the distance is halved. At some point the jammer is stronger than the satellite.

But even with a 1kW transmitter and an antenna with a significant gain, the jammer is not going to cover a large radius unless operating many distributed transmitters. This is practically feasible but not useful for the goals of the jammer.

With a jamming station on the ground, a potential solution for an aircraft in altitude is to use a more directional GNSS antenna shielding sources with a low elevation. Shielding is done by using choke rings. This type of antenna is commonly used on fixed stations to eliminate GNSS signals reflected by the ground or the buildings.

(Source.)
However this might also shield some satellites and decrease position accuracy. Satellites with a low elevation are useful to limit the dilution of precision.
With airborne jamming, the situation is different, but the solution is similar, instead of using a mechanical shielding, the receiver uses beam forming/steering techniques to eliminate certain solid angles from the radiation pattern of the receiver antenna. Such solution is sold, e.g. by Thales under the name TopShield.
On the other hand, for civil aviation, having the GNSS jammed is definitely not big business. GNSS are not the only navigation systems in the cockpit, navigation was possible prior to the advent of the GPS. An aircraft can use its 2 or 3 inertial systems to fly and reach an airport equipped with an ILS without GNSS positioning. The accuracy of the inertial system decreases with as time passes, but this is not a problem when the jammed area is limited, which is always the case.
Limited jammed radius
As a matter of fact, current jamming activities are local, mostly Russian Federation hampering precise Ukrainian strikes (map width is about 5500km):

(Source.)
To begin with, commercial aircraft are not likely to enter these conflict areas, but if they did, they can easily navigate 10 or 20 minutes without any GNSS position. This poses absolutely no threat to the aircraft or the other aircraft.
DSP and M-Code

Can commercial aircraft be equipped with ECM and ECCM equipment?

In theory digital techniques in the aircraft could help reduce jamming effects using more intensive (hence slower) processing (DSP), and extracting required information from partial navigation signals, e.g. missing the ephemeris or the almanac information but having the atomic timestamp from the satellite.
However this is not worth the effort for civil use, the crew just switches to inertial systems which are sufficient to navigate. If you're interested you can read this article, the style is a bit dramatic but there are interesting figures.
Military have other needs and will use the future M-Code signal on the GPS constellation L1 and L2 frequencies, the project has been delayed several times.
Contrary to existing codes, M-Code is not broadcast over the whole Earth hemisphere, but M-Code is not only broadcast over the whole Earth hemisphere, but also beamed to a specific area using beam forming on the transmitter antenna. It is thus 20 or 50 times more powerful in the selected spot, making the task of the jammer more difficult. In addition M-Code will be usable even if existing C/A and P(Y) codes are themselves jammed or made inoperative by the US. (Thanks to @nanofarad for fixing my approximation!)
I'm adding some generalities about GNSS jamming.
GNSS jamming principles
The principle of GNSS jamming is to flood the spectrum around the frequencies used by the GNSS satellites to broadcast their navigation messages.

The main US GPS frequency L1 on which the navigation message is broadcast is around 1.6GHz. L2 also contains a civilian navigation message, and L5 is entirely civilian.

L5 has been designed to resist some interference, with twice a transmitting power and a longer pseudo-random sequence.

(Source. See signals carried on these frequencies here)
GNSS transmit their message from 20000km with a low effective radiated power spread over a large bandwidth, resulting in a very low power density per Hz. This is by design. This way the signal is perceived as thermal noise. Reception requires digital correlation with a known pseudo-random sequence. Modernized satellites (block III) are a bit more powerful (300W EIRP instead of 50W).
This principle has a downside: It can be flooded from the ground easily. This is what happens when a receiver is jammed. Note the worst case is not when the signal is jammed (unusable) but when it is spoofed (usable but not genuine) and appears valid to a receiver while it contains a modified navigation message, leading to a position error.
While transmitting on the same frequencies, some satellites may still be usable when other are perturbed. The reason is the relative position of the satellite, the jammer and the receiver, and the spread spectrum which portions might still be accessible.

A spoofed GNSS signal can be detected by the integrity check (RAIM) associated with the receiver, and the satellite can be rejected.

A jammed GNSS signal is not usable at all.

In both cases the original signal cannot be recovered. In some case L1 frequency can be jammed while L5 is still usable. Both signals contains appropriate civil navigation messages.

[comment removed - couldn't find the original source I thought I was remembering]

@nanofarad, thanks for the information. You're right, it's also in the linked MITRE document: "This allows for a lower power signal with wide enough angular coverage for earth and space users (termed the earth coverage signal), in conjunction with a higher power signal transmitted in a spot beam (the spot signal) for greater
antijam (AJ) from space in a localized region. I did not read it entirely.

Ah, right, I just found that same MITRE document in my bibliography and it helped jog my memory. Thanks! (for future readers, since I can't edit my original comment after 5 min, it was just confirming that M-code is both a spot beam and a wide beam)

ECM is electronic countermeasures. It is defensive in nature. It is equipment designed to protect the aircraft from weapons. while chaff strips to protect against radar and flares to protect against heat seeking devices are not electronic they often are considered ECM. Some airlines such as El Al have carried IR strobes intended to protect against heat seeking or IR guide missiles. Less is know what if any protection they have against radar guided missiles. It is possible that other commercial aircraft could carry such equipment, but if they do they do not advertise the fact.
ECCM is electronic counter counter measures. equipment designed to make ECM less effective. This is not defensive in nature, so it is doubtful any commercial aircraft would carry any such equipment. Examples of ECCM would be a filter on IR seeker to look for the frequency produced by the engine heat instead of the higher temperature heat from a flare, or using doppler radar to detect speed to distinguish a moving aircraft from stationary chaff.
As other have mentions neither ECM nor ECCM would allow a jammed GPS signal to become readable. IN theory a highly directional antenna might allow you to detect the GPS signal, but given how weak the signal issue and the uncertainty of satellite positions this would not be very practical.

A suitably large patch array antenna could be steered with high enough directional sensitivity to listen to a selected GNSS satellite while rejecting low-altitude interference. This would be considered ECCM, since GPS jamming is in principle ECM. So anything you do to counteract ECM would be ECCM by definition.
On the ground, steerable dish antennas can do the same, and that's done to extract encrypted code sequences to allow the use of high-chiprate signal as a higher resolution reference for local augmentation and such.

"On the ground, steerable dish antennas can do the same [...] to allow the use of high-chiprate signal as a higher resolution reference": I think a GNSS steerable antenna must be an electronic array. A moving antenna with a reflector introduces PCO instability and multipath (and SBAS satellite out of sight) incompatible with high accuracy.


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Can I get an ATPL if I have two drinking-and-driving offenses in the UK?
Can I get an ATPL if I have two drinking-and-driving offenses in the UK?
I am thinking of becoming a pilot and a would like to know if there is a possibility (of course, after a period of time, and of course a lot of training).

Now this is why regulations are a Good Thing in aviation.

why would any airline trust a repeat drink driver to fly for them? Or indeed to perform any function with any responsibility.

@jwenting If they can get a medical certificate saying they’re now sober (which usually includes monitoring to prove they’re staying sober), why not? They’re arguably less of a risk than pilots who still drink.

Alternatively, one might argue that their decision-making skills are not sound.

@StephenS, a medical certificate saying they’re now sober?  Do AMEs grant such a thing?

@MichaelHall That’s the entire point of the FAA’s HIMS program.

@StephenS, maybe expand that into an answer then?  I know the ask was specific to UK, but that would be good supplementary info.

@StephenS an addict will forever be a risk, I KNOW that alcoholism doesn't go away if you don't drink for a few weeks. My mother was an alcoholic, it was a struggle for the rest of her life to stay off the booze after we got her sober, and the only reason it worked at all was because she was completely dependent on us, being wheelchair bound, and couldn't get any more booze in the house. Was hell on my dad who missed his 1-2 glasses of cognac a week because of it, but better that than have mom drink the entire bottle in a few hours and want more...

@jwenting A few weeks? FAA HIMS requires a minimum of six months proven sobriety to reapply plus another six-plus months for them to process the paperwork, and the alcoholic/addict most continue random testing for as long as they continue flying. The resulting lifetime success rate is 88%. What you may know about other programs (such as AA/NA, which admit a six-month success rate of only 3%) does not apply.

It's not the gaining of an ATPL that is the problem, so much as getting the medical certification to do so.
The UK CAA guidance material on alcohol/substance misuse can be found in this pdf.
It basically states that any conviction for alcohol/substance misuse should be "Considered unfit" - this does NOT mean you will not be issued a Class 1 medical, the notes state

If diagnosis, use or misuse is uncertain (e.g. first drink driving conviction and has had a clinical review by AME) fitness may be maintained
after discussion with a Medical Assessor at the CAA. A 3rd party notification or allegation should be investigated - discussion with the individual/informer/AME/GP

So, like almost everything with aviation  medicals, the answer is to discuss it with an AME - certainly before commiting a large amount of time or money to flight training.


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What is the difference between Level Change and ALT INTV during VNAV descent?
I'm confused between the two. During descent for 737 PMDG, I usually start a descent via ALT INTV, but sometimes the plane doesn't response to ALT INTV but responds to LVL Change instead.
I need help to understand the difference.

Could you explain what exactly you mean with "doesn't response to ALT INTV"? If your target altitude is below current altitude in VNAV descent, than ALT INTV should always allow you to descend. Are you sure VNAV descent is active?

Altitude Intervention will start a descent only if VNAV is the active mode (and the MCP altitude is below the current cruise altitude). If you're in Altitude Hold, then VNAV isn't active, and the Altitude Intervention button won't start a descent.
On the other hand, Level Change is its own mode, and selecting it (with a different altitude set in the MCP than what you're at) will always produce a change - either climbing at climb thrust, or descending at idle.  In both cases, flying at the speed set in the speed window.
VNAV is complicated, because while modes like Level Change, Vertical Speed, Altitude Hold, and GS Capture do "this," where "this" is a single easily understood thing, engaging VNAV means that we've given control to the computer logic, which can do lots of things. And we have to have an understanding of that logic to understand what VNAV will do. The Speed Intervention button and the Altitude Intervention button are inputs to the VNAV system only; VNAV also considers the altitude window and, when it's open, the speed selection. And of course VNAV uses what we've entered into the FMC as well.
For all its complexity, VNAV is one mode; Level Change is another.  To start the descent, Level Change will always do it, but then you aren't in VNAV with its various features (such as meeting the speed & altitude constraints in the LEGS page). If you're level in Altitude Hold and wish to start a descent in VNAV, then you should select VNAV & observe that the FMA changes to show VNAV as the active mode. Now, Altitude Intervention will work, as well as "Descend Now" on the CDU's Descent page.
The key is knowing what mode is active - and that's on the FMA. If Altitude Hold is active, you'll have to change the mode to start descending. You might change to Vertical Speed or Level Change to start down right now.  If VNAV is active, you have the tools which that mode gives you to control your path, and you can also select a different mode too (useful if VNAV isn't doing what you need the airplane to be doing right now).
In line flying, we'll generally prefer to stay in VNAV as much as possible, so if I'm at cruise altitude in Altitude Hold, I'll generally engage VNAV. Thus, I can control our cruise speed via the FMC, and when I'm given "descend at pilot discretion..." I can set the MCP altitude to the new clearance, and let VNAV manage the descent - starting it right at the calculated Top of Descent, managing the speed thru the transition from Mach to IAS, meeting step-down constraints on an arrival, etc.
There are times that the other modes are useful; for a 1,000' climb or descent, Vertical Speed at 1,000 FPM is a more gentle ride than going to full climb or all the way back to idle, and for "descend now to FL xxx and give me a good rate" then Level Change fits the bill.
Mostly, though, VNAV is what's active.

Many thanks. In summary, the key is to know that mode is active, if Alt Hold is active, use VS speed or Level Change. If VNAV mode is active, use ALT Intervention for descent.

@Billcoke Not necessarily: if ALT HOLD is active, you should press the VNAV button first, then select a lower altitude and press ALT INTV. This is the preferred way to initiate a descent in the 737. You would only use V/S or LVL CHG if you specifically need them for some other reason.


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Where do countries under international sanctions find spare parts?
Some countries are being touched by American or European sanctions. Such sanctions affects the possibility to import spare parts for American-made or European-made aircrafts (e.g. Iranian F14 and Venezuelan F16 or Puma). Yet these countries still have their aircraft flying.
Where do the sanctioned countries find their spare parts?
Do they still follow the required MRO process?

In the case of the Iranian Tomcats, as far as I'm aware the answer is "They get spare parts by cannibalizing their other aircraft."

Are you limiting this to military aircraft, or are civilian planes in scope too?

@StephenS I guess commercial planes can have their maintenance in an airport outside the country. However military planes usually can't (expect during operations).

I think people make too much drama out of the F-14 parts embargo. These are aircraft the US themselves have retired because of fatigue and cost of maintenance issues. Iran really only flies them if they want to publicly thumb their noses at the US. The country is quite capable of sourcing much more advanced aircraft from other countries who could care less what the US government thinks about that. They also modify older airframes to produce their own versions of aircraft. Iranian engineers are quite capable of this. The ones living in the US have proven that beyond any doubt.

In the case of military planes, they could try convincing someone with parts to secretly violate the UN sanctions, which may not be difficult if they have something the other really wants, like cheap oil.
If nobody has parts or those who do can’t be bribed, such as the case of Iran’s F14s, then you cannibalize planes until you run out of critical parts, and then the entire fleet is grounded. That is, after all, the goal of the sanctions.
However, for civilian planes, like North Korea’s state-owned airline, there is a humanitarian exception to the sanctions to keep their planes airworthy—mostly so they don’t crash and kill innocent people on the ground in other countries.
Keep in mind that sanctions apply to anyone doing business with that country, even outside of its borders. They can’t just fly their planes somewhere else for maintenance to get around the sanctions.

The consequence of sanctions on Arpartheid South Africa was a thriving military equipment sector with some remarkable products, including nuclear weapons. Simply put, other people are clever enough to find equivalent solutions to US engineered parts and only when a super expensive fab costing billions is needed will they need to downgrade their specs. But don't think that sanctions will in the long term keep other countries from owning fancy equipment: They will learn to build it themselves.


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Why are some ATP CTP providers not on the FAA's approved list?
The FAA has published a list of ATP CTP provider schools. But I can still find other schools not listed in this list, like "ATP flight school".
I'm sure that only approved facilities can provide an ATP CTP course. What's happening here?

The FAA's ATP-CTP Advisory Circular 61-138 does not prohibit a qualified ATP-CTP instructor using an approved training program from delivering the training at any facility that is willing to pay for their services.


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Are there any places I can take an FAA written test in Japan?
I want to ask FAA in person. But, I was not able to reach them. I tried phone call 8668782498, sent e-mail to local FSDO. But nothing coming back.
I guess I have some possibility to take it in military base placed in Japan.
Do you know something about this?

According to this list, there are three Airman Knowledge Testing Centers outside the 50 states (listed as "Out of US" on that document.)  All of them are in US outlying territories, and none of them are in Japan.
You could conceivably arrange do the written test at the center listed in Guam (Barrigada).  There are regular airline flights to Guam from Tokyo, Osaka, Fukuoka, and Nagoya, and the 4-hour flight to Guam is better than the 8-hour flight to Hawaii or the 9+ hour flight to the continental US.

Thanks, if I need, I'll take it. Because nobody knows this...


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Is it normal for instantaneous GLOC to occur at 5 G's?
Is it normal for a trainee to have an instantaneous G-force induced loss of consciousness (GLOC) at 4-5 G's in a light military trainer aircraft like Socata TB 30 Epsilon, after doing a manoeuvre sequence?

Did you follow your training and were you wearing a G suit?

Wasn't me but a comrade who started training about 4 months ago. In Portuguese Air Force trainees don't wear anti G suit in this formation phase and in that particular aircraft. He did AGSM, but i cannot be sure if correctly executed...

That sounds really unlikely to be a G-LOC.  That usually happens at much higher loadings after 3-4 seconds of straining.  The counscious and cognitive centers of the brain take a few seconds to shut down once the systolic and diastolic pressures hit zero in the brain.  It may be an indication of another underlying medical issue.

I agree that doesn't sound normal.  I didn't strain unless I was pulling in excess of 4 and never experienced any ill effects.  I also never had a student GLOC and we would pull north of 6g's pretty routinely.  They should definitely be checked out medically.
I will caveat this because you used the word instantaneous.  It would not be unusual in my opinion for your student to go to sleep if they were pulling a sustained 5g's and were not correctly using their g-strain.  Every person's resting g-tolerance is different, and can be higher or lower on any given day based on a lot of factors.

Normally, there should be signs of oxygen deprival before full loss of consciousness. In my experience, first the field of sight narrows down as if someone drew a curtain in the eyes (tunnel vision), and then you go totally blind. This would happen to me at maybe 1 g less than usual when preceded by inverted flying, but still only above 4 g. Hearing and reasoning are not yet affected - for this it needs more gs.
How many depends on how long the load factor lasts and on general health. Training also helps, as do breathing techniques like the anti-g straining maneuver. From an FAA brochure on this topic:

This is a physical technique where the aviator pushes air out of the lungs against
  a closed glottis, while simultaneously contracting
  the muscles in the calves, thighs, and shoulders.  is resistance inhibits the blood from  owing away from the brain, and it simultaneously increases the pressure in the carotid arteries.

Instantaneous G-LOC is only possible with very rapid rates of g increase to a level above 6 to 8. At 4-5 gs this should not happen to a healthy person. I would recommend to see a physician about this.

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text:
Why are some seemingly major waypoints nowhere to be found on sectionals (including enroutes)?
I'm looking at the BNTLY.CAVLR3 arrival at KIAD:

Almost none of the waypoints (BNTLY, CAVLR, COINZ, etc.) are on a single sectional or chart, enroute or otherwise. Considering this is such a major route into such a major airport, why would these waypoints not appear? How would one ever hope of finding their location?

It might help to put it the other way around: why should every waypoint appear on every chart? Different charts are used for different purposes and have very different scales. Also keep in mind that sectionals are for VFR use, whereas an arrival is an IFR procedure.

Fair enough, but I'm not seeing these waypoints on the the Enroute-Highs, Enroute-Lows, the TAC, the World-High, or the World-Low. As far as I can tell, no chart exists or is immediately available to show at least coordinates for these waypoints. Is it assumed that you'll be able to load them out of a GPS database? That doesn't sound right, considering they predate GPS.

Yes, that's an RNAV arrival, which in most cases you can simply consider as GPS. The waypoints would be loaded from a database when the pilot loads the arrival procedure into whatever avionics (e.g. GPS or FMS) he's using.

The CAVLR3 is an example of an RNAV procedure. A requirement to fly an RNAV procedure is for the aircraft to have navigation equipment capable of finding all of those points. There are many thousands of those waypoints, and it would create way too much clutter to show them all on a chart.
For a pilot planning on flying the CAVLR3, the Enroute H-10 chart can help them find the transition waypoints DORRN, THHMP, and TRSSK. Once they reach a transition, the approach chart covers the remaining route.

If the aircraft does not have the equipment to fly an RNAV approach, they would use a non-RNAV procedure like the COATT4. This follows fixes and VOR's, which are all included on the Enroute L-36 chart.

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text:
What means of navigation did commercial Soviet airplanes use in the 50s-90s?
Nowadays, practically all Western commercial airplanes use some kind of GNSS/GPS as primary means of navigation, sometimes paired with inertial navigation systems and user-friendly computer interfaces (FMCs). This allows planes to follow very precise routes in long flights, also shortening flight times by flying more "direct" routes. Before the 1980s and the use of GPS in civilian aircraft, instrument navigation was pretty much all about VOR/DME/NDB.

How about the Soviet aircraft built between the 1950s and the 1990s? How close were the Soviet navigation systems to the Western ones, and what were the major differences?
It's common to see a "navigator" position in Soviet aircraft cockpit videos. Was it so complex that it required an extra crew member?
Did the Soviets ever get to use GPS navigation or at least FMCs in their planes?

GPS, in the form of NAVSTAR, has always been a US, and first and foremost military, system. Present-day Russia has its equivalent, GLONASS, though I'm not sure when that became operational. (EU has Galileo.) The odds that the US military intentionally shared GPS technology with the USSR seems slim, given the system's obvious military applications.


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Single Engine operation on Twin Engine aircraft
I recently came across ETOPS and I wanted to know:
How does a twin-engined aircraft  balance out the lack of thrust on one side in the event that one of the engines is non operational? Any information is appreciated.
Apologies if this has been asked before or if it doesn't comply with other standards. I'm new around here and couldn't quite find anything that addresses what I wanted to know. If someone can point me in the right direction, I'd appreciate it.

related: https://aviation.stackexchange.com/questions/17256/what-would-happen-if-one-of-the-engines-failed-during-takeoff-and-other-engine-i

@jamiec that helps a lot lot. thanks.


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Calculating the maximum altitude of a drone
Is there an equation to find the maximum altitude that a drone or quadcopter can fly to ?

In the US, drones are required to stay in visual range.  How far away can you see?
There is also a free AOPA app that you could look into to help keep you out of trouble (or form hurting me as I fly around in my airplane at 145 MPH trying to keep an eye out for smaller things like birds and drones):

B4UFLY is an easy-to-use smartphone app that helps unmanned aircraft operators determine whether there are any restrictions or requirements in effect at the location where they want to fly.
Key features of the B4UFLY app include:
clear "status" indicator that immediately informs the operator about the current or planned location. For example, it shows flying in the Special Flight Rules Area around Washington, D.C. is prohibited.
Information on the parameters that drive the status indicator
A "Planner Mode" for future flights in different locations
Informative, interactive maps with filtering options
Links to other FAA UAS resources and regulatory information

Re visual range, I could quite easily strap a drone to my backpack and hike to the summit of Mt Whitney, Pike's Peak, or many another 14K ft mountain.  So would the drone be able to take off at that altitude?  (I once was given one of those little toy electric helicopters, which would hover in the Bay Area's sea level air, but not at my ~5000 ft home.)

I don't know.  The electric motors are likely expecting a certain amount of resistance from the prop pushing on air, which in turn has an impact on current flow. The ESC in the drone may limit the speed the motor can turn (RPMs). With the less dense air, the props can spin freer and the motor might overspeed or overcurrent if not limited by the ESC. If the ESC does limit the RPMs or current, than maybe you could use blades with more pitch to make up for the less dense air and still be able to fly.   A nonturbonormalized gas engine loses HP with alititude, I'd have a hard time getting to 14K.

I was flying this morning, having to pick out a 34' wingspan/30' length aircraft 2 miles away to follow in for a landing. I knew what I was looking for and where, and it was white moving 100 MPH against a green trees background.  I wouldn't be able to pick out a 2-3 foot drone barely moving (relatively) that far away.

It's not just a matter of power, it's that the less dense air produces less lift per rotation, and of course there are going to be purely mechanical limits on the max speed of an electric motor.  (Non-turbo'd piston aircraft get a double whammy, of course.)  But my point was that if your drone could fly from the summit of a fourteener, you'd have no trouble keeping in visual contact, while 14K ft from sea level would be a different story :-)

Try different pitch blades to make up for the lower density, or perhaps larger diameter or wider chord.   If you and the drone are both at 14K, then yes I suppose you'd be able to keep it in sight.


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What drives the shape of an engine's intake on a fighter jet?
Rectangular intakes have more corners which might increase subsonic pressure losses and would weigh larger than a pitot (Semi-circular) type intake. Are the designer drivers solely based on supersonic pressure loss improvement? Or for area-ruling? Am I missing something here?
F 16 has a pitot (Semi-circular) type intake whereas JAS 39 Gripen has a rectangular one. I wonder why.
Edit: The question is in reference to a fighter aircraft intake which employ fuselage buried engine configuration in-contrast to wing mounted or externally integrated engines.
Fighter aircraft intakes are more complex when compared to simple cowl-lip configurations designed for larger commercial engines.
Intake shape,size,location are function of wide variety of parameters, so something must be influencing the intake entry cross section of a fighter aircraft configuration.

@ymb1: While I agree that this is a dupe, the answers to the original question might not be sufficient.

A reminder: if you have answers, however partial, please post them in the answer field.

Are the design drivers solely based on supersonic pressure loss improvement?

Yes. And sometimes a few more considerations need to be taken into account.
We have covered the reason for intake shapes well on this site, but the details must be collected from several answers. In a nutshell: Higher flight Mach numbers need more elaborate and heavier intakes in order to convert the kinetic energy of the flow into pressure. A pitot intake is light and simple, but a poor choice for speeds in excess of Mach 1.6.
Rectangular intakes are normally chosen in order to make internal, moveable ramps possible which create a cascade of shocks in order to slow down the flow as efficiently as possible. Such designs are typical for Mach 2 aircraft (think Concorde, F-14, F-15, XB-70). Another way would be a central intake with a moveable spike, but those had to make way for big radar arrays in more modern designs. The JAS-39 intake is a little special: It sits next to the fully moveable canards, and those need a vertical wall in order to minimise the gap between canard root and fuselage/intake structure. Yes, a round intake would be slightly lighter, but is impossible due to the situation of the canards.

Detail of JAS-39 canard, taken from this picture.

Another reason is stealth - the shapes can be selected to minimize radar return. See the F22 and F35 leading edge shapes for example.

You have the right idea when you discuss area rule (Coke bottle) shape and pressure/compressibility.  A classic example of the area rule shape for supersonic flight is the T-38/AT-38 and it's big brother the F-5.  A large part of the limitation on the T-38's flight envelope is the air entering the engine.  I have flown it up to Mach 1.3 which it can do reliably, however to go beyond that up to M 1.5 requires a very narrow range of temperature and pressure altitude due to the susceptibility to engine compressor stall and flameouts above 1.3 , due in large part to the supersonic airflow entering the intakes.  The F-16, mentioned above, not only has a semi-circular (shark's mouth) intake, but also a large curve inside the intake (like a slide at a kid's park, slopes up as you enter the intake) and there are actually two flavors of intake for the Viper depending on the engine (the smallmouth and largemouth intake), the very long version of which is here:  https://arc.aiaa.org/doi/abs/10.2514/3.22758?journalCode=jpp

From what I could find, the rectangular geometry of fighter aircraft intakes is due to the fact that the intakes incorporate sharper inlet lips in order to decelerate airflow to subsonic speeds to avoid supersonic performance losses from shock waves. There are some aircraft such as the MiG-21 and SR-71 which use adjustable inlet cones in order to be able to cruise at higher speeds without significant performance losses. According to Wikipedia, the MiG-21's inlet cone allows the creation of two shock waves, both of which are aimed at the inlet lips.
As for the F-16's semi-circular inlet, I'm not sure why that is the case. I couldn't quite find any helpful info.

https://www.grc.nasa.gov/WWW/k-12/airplane/inlet.html This Nasa link does a decent job of simplifying why inlets are shaped differently for different speeds.


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Could two GE9x engines power a 747?
These new GE9x engines are huge and extremely powerful, but could two of them power a B747–8?
It is possible for some engines to power the original 741s but I am mainly interested in the B748.

I think Therac's  point about engine failure requirements is the biggest problem with re-engining the B747-8. With four engines, a single engine failure results in a 25% reduction of power, but with two massive engines, thats a 50% reduction, so the single remaining engine would have to be able to climb the entire 447 tons. Its not enough for 2 engines to match the take-off power of 4 engines.

The 747 Hydraulic and Electrical systems would also have to be redesigned to allow for single engine redundancy.

The curently operational GE90-115B engine is somewhat more powerful than the listed specs I've seen for the GE9X, at 115,540 lbf thrust vs just 105k.
That engine powers three current variants of the 777. Interesting to note that the 777-300ER is actually 5% heavier than the original 1966 version of the 747. Two of the 90-115 also have more takeoff thrust (~230k lbf) than the original 747-100 (~175-205k lbf).
So, in theory, two modern engines can power a 747, but only the original, not the 747-8.
Twins have higher thrust requirements, as they have to be able to take off with just one engine, while quads can use three. The 741's wings aren't as effective as the 777's, so even the 741's 5% lower weight might not quite suffice. But as the "741-twin" could use less fuel than the original, it could still maintain the 741's original payload and range.
There are other changes required for a twin and for ETOPS, so it won't be just a re-engine. All in all, a twin-powered aircraft with the early 747's fuselage, general layout and performance, but some control modifications, should be possible.
The 748 is a much heavier aircraft than the 741. It could in theory be ferried with the power of two GE9x engines, but its total weight would have to be restricted to less than that of a 741. That cuts its useful load in half - essentially, half the aircraft is now useless.
If operated, it wouldn't be able to fill all its seats or fly its full range. Such an aircraft would have no value for commercial operations. The only uses for it I can think of would be an oversized vomit comet or carrying something extremely light. And there are special aircraft with oversized fuselages for that like Airbus Beluga or Boeing Dreamlifter.
The minimum a modified 748 could operate commercially with is three modern engines. With two out of three GE9x running it would get 210,000 lbf of thrust, which is marginally above the 200k that three of the 748's engines produce.
TL;DR version: Two GE9x could keep a 748 in the air, but not in the black.

The question was specific for the 747-8. You mention the 747-100 in your comparison, but it is significantly smaller and lighter than a 747-8 (333t vs 447t MTOW, thats a 34% increase in weight). Also if a 747-like aircraft would but feasible with two engines then why does the A380 still use four?

There are two questions: "Could two of the GE9x power a 747" and a more specific "could two of them power a B747–8". The answer to the first is yes, to the second is no. The A380 is further much larger than the 747, it's not really 747-like.

The 747-8 uses four GEnx-2B67B engines  for a total maximum thrust of 296 x 4 = 1184kN. The GE9x is still under development but should provide 470kN. With two engines that amounts to 940kN, which is not nearly as much as the four engines of the 747 provide.
Would a 747-8 by able to fly with the power of two GE9x engines? In theory yes, but with less cargo capacity and a lower MTOW as the engines are less powerful. However in reality a 747 will never fly with two engines because the airframe and the wings are not designed for it.

I agree 21% decrease in trust is a big issue but using only two turbines can save a lot of weight in wing structure, pylon and the turbines themselves, together with a possible fuel reducion and a little less drag the performance decrease can be a lot "better"

Two GE9x actually weigh as much or more than four of the original engines. They're much bigger. Plus, their weight and thrust are spread over fewer points, which is a bit less structurally desirable.


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Are the flaps of a Cessna 414A fully extended at 15 degrees or at 45 degrees?
When are the flaps of a Cessna Chancellor fully extended? At 45 or 15 degrees? Also, what are the range marks of its tachometer with Continental TSIO-520-NB engines?

Full flaps at 45°.  Normal range of the tach is 2100 to 2700 rpm.  TCM has since published a service bulletin recommending no less than 2300 rpm in cruise due to issues with crankshaft counterweights.
The numbers on the face of the tach represent the first two digits of the rpm value.  When the needle points to "25" the rpm is 2500 rpm.  Each small mark between the numbers represents a value of 100 rpm.
Using ymb's image:

The other gauge (manifold pressure) has numbers hatched into the panel to designate maximum manifold pressure at high altitudes.  The "20" represents maximum available manifold pressure 20,000' (about 36"), for example.  As the plane climbs, the maximum possible power setting falls.  Those markings assume a well maintained turbo system, of course.

I assume the flap takeoff position is 15 degrees?

With the exception of the 404, I never used flaps for takeoff in any twin Cessna as standard practice. I would not want to lose one with the gear and 15° hanging out in a 414 carrying any kind of load..."yer gonna have a bad time." I believe all of the 300/400 twin Cessnas use draggy split flaps except the 404 and a handful of modified R/STOL 310s which use fowler/slotted-fowlers.

Follow up: I just flipped through the 421 normal procedures. It calls for flaps up on takeoff. I don't have a copy of 414 procedures handy but I'd be surprised if they were much different. I recall them being very similar.

Which 421 model? Early 400 series all used a simple split flap. Later versions like the 4141A and 421C used a more advanced type of flap.

I looked at a 421c manual. Manual indicates it's a basic split flap system (pg 7-15).  I'm interested to learn more, though.

I must have been thinking of the Robertson STOL fowler flap kits that were applied to some of these aircraft.

I did some digging after you responded.  I didn't know the R/STOL included 400 series twins.  I thought the 310 was the only option.  Cool stuff.

Are the KCAS numbers listed on the flaps control the stall speeds?

They are maximum speeds at which the flaps may be used.  Up to 160kts for 15° and up to 140kts for 30° and 45°.


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How can I calculate airfoil thickness?
Given this information...

... how can I find the thickness for a "NASA/Langley LS(1)-0417MOD general aviation airfoil" at 90% and 99% chord?

You have already done half the work. With the precise name it was easy to find the coordinates here and plot them. Yes, the coordinates look fine (no steps, no distortions)

Now either measure the thickness directly from the plot or subtract the lower contour point at 90% and 99% from its corresponding value on the upper side. You will need to interpolate between the two adjacent points, though.
Since you seem to need the thickness to calculate the lift curve gradient, you might just rely on the NASA technical paper which contains measurements and airfoil data on just this one airfoil. Be sure to correct for the proper Reynolds number and check whether your application uses the same thick trailing edge that is used in the coordinate file.

Thankyou verymuch sir, actually. what should i do to calculate thickness at Y90% chord and Y99% chord. how to calculate it?

how do i calculate with theorytical

because i was trying search used CAD to find value thickness at Y90% chord and Y99% chord. and i have the value, then i try equation at the picture. but the value of cl alpha be divided cl alpha theory more small from NACA 0015.

i mean how do i calculate use theoretical method to find value, thickness at Y90% and 99%.

@AdeFirmansyah: This depends on the airfoil. Most airfoils are shaped to yield a desired pressure distribution and the above mentioned method is the only way - there is no "theoretical method". This is also true for the LS(1)-0417. Old 4-digit NACA airfoils use a fifth-order equation for the thickness distribution along the chord, and there is an analytical method, but using the technique described above is easier.


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How do I find the three factors of the hinge moment coefficient?
How do I find the three factors $c_{h0}$, $c_{h\alpha}$ and $c_{h\eta}$?

Use eta ($\eta$) for deflection. Use XFOIL to determine the coefficients.

i apologize, may i have the tutorial XFOIL for calculate coefficient moment? actually i never use XFOIL. thank sir.

First download and install xfoil from this site
http://web.mit.edu/drela/Public/web/xfoil/
if you use ubuntu - sudo apt-get install xfoil
user manual and typical session inputs are also there. please refer to them as you haven't used it before.
And there are many video tutorials in youtube.
[Link removed I cant put more than 2 links here- Just search xfoil tutorial in youtube]
For this specific case;

open your airfoil in xfoil
xfoil name.dat
Set the flap as you want
enter GDES and FLAP and follow the prompts.
Type these commands in sequence
exec
[enter]
pane
Enter OPER menu and set the RE number
oper
visc 1e6 (1 million Re for this case)
type  these commands in sequence
hinc     (hinge moment togle enabled)
    pacc     (accumilate polar - give a file name)
aseq 0 10 0.5 ( sequence of alfa to run - here from 0 to 10 in 0.5 increase)
Open the resulting file. which has two coloums along with other parameters to show alfa and hinge moment. (first and sixth)

plot it or linearize it or whatever you like to do to find the above parameters.
PS: Another suggestion is XFLR5. It is same as XFOIL but with GUI. you may find it easier.


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Why do aircraft fly over land rather than over the Adriatic Sea?
When flying from central Europe to Greece or Egypt, I've noticed the plane often follows down the eastern coastline of the Adriatic Sea, instead of flying in the middle on a path I imagine would put less noise on the ground. Why is this the case? Closeness of emergency landing airports?

As far as I can tell, no airline currently flies from Innsbruck to Heraklion.  Can you provide an example of an actual scheduled flight that takes the sort of route you're describing?

@MichaelSeifert it's much easier to look at Athens. Even the same flight numbers aren't consistent with this though.

the picture was just for illustration, but e.g. WK 131

Noise is'nt really an issue when cursing

@Antzi it depends how loudly you swear

Most air routes in Europe are unchanged since the days before GPS, when they were defined by radials from VOR and NDB radio beacons. As these have a limited range, they could easily be used to define routes across the Adriatic, but less so down its several-hundred-mile length. Routes would therefore normally be defined over land where the plane can route from beacon to beacon, rather than over the sea where (unless you are flying towards or away from a coastline) you cannot fly with as much navigational precision as when following a radial to/from a beacon.


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What's the difference between a Terminal Control Area and a Control Zone?
From what I've understood, in Canada a Terminal Control Area (TCA) is established at airports with a high volume of traffic to provide IFR control service to arriving, departing and en route aircraft.
A Control Zone is designed around aerodromes to keep IFR aircraft within controlled airspace.
Why do we have both? Both provide ATC services, so why do we require a Control Zone within a TCA? Is there a specific reason that the TCA cannot be lowered below 700 AGL?
See this reference material in "From The Ground Up" (I've tried to attach it but it didn't work).

If you're using From The Ground Up, you're asking about Canadian Regs?  They are largely similar, but there are subtle differences between Can and FAA Regs so it's important to make the distinction.

@JohnK The OP used the "canada" tag, so I'd say that they are talking about Canadian regulations.

A Control Zone is the small (and usually circular) surface area around the airport that is handled by the airport's control tower. At smaller airports (but still large enough to have a tower), this is all they have.
A Terminal Control Area is a large and typically complex area above one or more Control Zones to manage large flows of fast traffic (i.e. airliners) moving in both directions through the congested area between the Control Zone(s) and the en route environment far above.
Note that while Canada (and the US, though it uses very different terminology) often uses the same class of airspace for the TCA and CZ, that isn't required, and there may even be several CZs with different classes under one TCA.

Important point: a control zone always touches the ground, a terminal area does not.


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Do turnbuckles twist the flight control wires?

When adjusting a turnbuckle on any flight control, we usually use a wrench and turn the hex shaped section of the rod end inserted into the turnbuckle barrel. That flight cable from the turnbuckle is connected to a stationary non rotating component, but when we turn it aren't we just twisting it at that point, which causes stress loads on it.

Yes the cables can be twisted if proper care is not administered during tightening. There are tools that allow for tightening the buckle while keeping both ends untwisted. From this article:

Cable tensions are adjusted by twisting the turnbuckles that connect different sections of cable together. It’s a simple system, but you need to hold each cable end stable while turning the turnbuckle in order to avoid putting twisting stress on the cable itself. If you work alone, you may want to invest in a cable turnbuckle tool that holds both cable ends stable while you twist the turnbuckle barrel.

One bolt has a left-hand thread and the other with a right-hand thread:

Source
If you lock both wires and turn the common nut (barrel) no twist is added to the wires. This is the proper way to proceed. With someone to help, this can be done easily, but you may use a tool to lock the ends and turn the barrel.

simple wire is good for this if there are holes in the wire end devices:

Source
The chain rig kit. One hand to turn, one hand to pull the chain:

Source
Also this style:

Source


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Does full nose up trim yield best glide in Cessna 172/152 for a given load?
I heard from a ground instructor that full nose up trim will yield best glide in a 152 and 172.
As I understand best L/D, a lighter loaded plane will require a slower glide than the same craft loaded more heavily.
Am I correct in thinking that the best glide in the POH is an average glide for an average load?
Was my ground instructor correct? Those extra feet may be useful one day!

I'm not sure that it does, in the 172 when practicing engine-outs I would have to trim nose down to achieve best glide.

I don't think the POH refers to "average glide" and "average load".  I think almost all of the POH is written for Standard Temp & Pressure (STP) and max-weight.

Interesting to hear the POH  best L/D is for max load, presumably then a slower speed is would yield a  better glide distance if well under max load. I wonder where my ground instructor got her information from! It was an aside from a class sometime ago, so cant follow it up. Perhaps this is something I need to experiment with using a GPS and a hard deck!

That ground instructor is giving you bad information. You can not make a blanket statement like "full nose up trim" and expect it to be valid for any and all situations.
You are correct that the best L/D speed will yield the best glide ratio and that the speed will vary with weight.
The best trim position is the one that will maintain the best glide speed hands off. Any other trim position will require an additional control input to fight the trim and that input will cause additional drag.
So no, full nose up trim will not yield the best glide unless by some remarkable coincidence that is also the trim position for hands off best glide speed.

From my personal experience, I believe that full up trim will be close to Vbg, but not exactly.   In an emergency or high-workload situation, it may be pretty good to just set full trim, and not worry about being off 2 or 3 kts.

But what if the aircraft is loaded so the C of G is at the rear limit? Would you still blindly dial in full nose up trim and hope for the best?

Common sense always applies.   I mean in a typical situation.  I would not normally fly near max Arm limits.

Flying properly trimmed is more efficient in aircraft in aircraft with trimable stabiliser. But C152 and C172 have just trim tabs, so it does not apply.

Your instructor was correct in that full—or nearly full—nose up elevator trim in the Cessna 172 will give you roughly best glide speed. This is a rule-of-thumb and must be understood as such.
Variances in aircraft CG and even trim rigging render it impossible to make statements such as "X trim setting will give Y speed." And we should note that the best glide speed varies by weight. The Cessna POH or AFM will only give best glide speed for max gross weight.
However, within these limitations, trimming close to full up will get you close. This can be a very helpful rule-of-thumb to get your aircraft quickly trimmed very close to where it should be before fine tuning the trim setting, such that you can glide hands off or with minimal elevator input. This can be very helpful to minimize task saturation when dealing with an emergency, simulated or otherwise.
Now, best glide speed, it should be noted, has a fair margin of error, both positive and negative, in which a change in airspeed will result in minimal change in glide distance. The L/D curve is such that a positive or negative speed variance from best glide speed will give minimal change in lift and drag, generally within a margin of a few knots for an aircraft such as these light Cessnas. For more on this and a visual representation of the L/D curve, see this answer to What is the definition of “best L/D”?. Practically speaking, if you trim full nose up and have the aircraft trimmed hands off to within a few knots of best glide, you are probably doing well. Don't use this as an excuse to be lazy, but don't allow yourself to become fixated either.
I should note that while I have a lot of experience in the 172, I have never flown a 150 0r 152 so I cannot speak to those.


text:
What are normal landing separation minima?
As far as I know we have separation minima of 10 minutes in horizontal flight, so do we have any equivalent separation minima for landing? If so, how it is possible to land two aircraft in a very short time, like 40 seconds? And doesn't this create wake vortices?

An air traffic controller won't land a Cessna 172 behind an Airbus A380 with a 40 second separation, usually they like to land the same class in short intervals to minimize wake turbulence issues. When changing weight classes, they will space them out further to allow the wake turbulence to dissipate. Really the biggest concern is getting the landing aircraft off the runway before the one on approach needs to go around.

Welcome to aviation.SE! You might want to check some of our existing questions about separation and wake turbulence: here, here, here, here and the separation and wake-turbulence tags

(Posting a reply to your "answer" below here) Yes, its very possible. Especially considering Dubai has parallel runways they can provide separation since the 43 seconds is total landings, not for an individual runway.

This is pretty well answered at http://aviation.stackexchange.com/q/26183/8730

To the best of my knowledge, there is no set time between aircraft recovery; just enough time for the aircraft type, approach speed, typical required ground rolls and time for the aircraft to taxi clear of the runway prior to the next arrival.  Usually for busy hubs in Class B airspace, spacing is kept to a minimum, sometimes even less than a minute between arriving flights.


text:
What is the longest range single-pilot certified (FAA and/or EASA) business jet?
I suspect the single-pilot business jet with the longest range is the SyberJet SJ30x:

NBAA IFR Range with 100 nm Alternate
M 0.76 (1 pilot + 2 passengers; passenger/pilot at 90 kg each)
2,575 nmi (4,769 km).

But I am not sure; also, there are many negative reviews regarding SyberJet company and its aircraft of which, by the way, only a dozen have been produced for now. Are there any single-pilot certified jet with longer range in comparison with SyberJet SJ30x?

Hello Max, welcome to Aviation.SE.

Thanks a lot, @DeltaLima ! Really happy to be here. But unfortunately I have very low English-ability.

don't worry about your English level. There are many people here that aren't native English speakers, including me. Overall I find this community is quite patient and helpful when it comes to understanding and improving questions. Just be as patient with those trying to help you and you'll be fine.

I used to ask this same question. That is, what is the longest range single-pilot aircraft? One contributor noted the potential for using ferry tanks to extend range. But, that contributor said it is not practical for regular use. If "practicality" is included as a qualifier, it would seem that the aircraft's own range is not the limitation. Instead, it would be the pilot's and/or passengers' personal range that would seem to be the limitation. That is -- in all seriousness -- how long between relief breaks? Even if an aircraft has a lavatory for passengers . . . although, not all do.

There are only a hand full of single pilot jets in production currently and the SJ30x seems to have the longest range by far. The other competitors in the space, the Cessna Citation Mustang, The Honda Jet and the D-Jet come in roughly in the 1300-1500 mile mark which is far less than the SJ30x.
Depending on how far you are willing to stretch the planes you include many military fighters, many of which you can own (which are generally single pilot planes) have a range that competes with or exceeds the SJ30x.
There is another caveat to this as well. All of these planes can in theory be fitted with ferry tanks which can greatly extend their range for a single mission. Its generally impractical to do this on a constant basis but it can be done in one off scenarios.

He didn't specify current production, so that means that there are other aircraft to consider as well...

There aren't any civilian, current-production jets that come close to the range of the SJ30 for single pilot operations based on my research, although one or two turboprops have comparable ranges. I consulted Aviation Week's "Business Airplane's 2012" and the only other light jets listed with a long range are the Embraer Phenom 300 with a range of 1,954 nm, and the Cessna Citation CJ4 with a range of 1,913 nm.  The Cessna CJ3 comes in at a respectable 1,869 nm. The PC-24, which is still undergoing certification in 2016, is listed here with an NBAA range of 1,950 nm. All of these are (or will be) single-pilot certified in at least one cockpit configuration, to my knowledge.
Is there any reason you're restricting this to jets and not turboprops? (Speed is one of the biggest differences between the two categories.) The King Air 350IER has a range of 2,239 nm.  Several other turboprops have ranges that are comparable to average light business jets, like the PC-12 NG which has a  range of 1,544 nm.
Here's a graph of my own making to show these statistics:

For any readers unfamiliar with the restrictions regarding FAA approval for single-pilot operations, here's a good source: http://www.flyingmag.com/single-pilot-jets . The biggest stipulation is that transport category aircraft (12,500+ lb MTOW or not commuter category) are assumed to be two-pilot aircraft.
Note:  all ranges listed here except the PC-24's range are NBAA IFR max fuel ranges w/ 100 nm alternate as listed in Aviation Week's "Business Airplanes 2012"

It should be noted that some of these planes are only certified for single pilot ops in certain configurations. For example the CJ3 requires a certain cockpit setup for SPO as specified in the type certification

@Dave Thanks, I corrected the inaccuracy.

The CJ4 is, with nearly 2000 nm. Some would say the SyberJet SJ30 but since you can't buy one yet the Cessna CJ4 is the winner in jets. And in turboprops the Beechcraft 350ER.

The SyberJet doesn't exist for practical purposes.  The design has changed hands through at least 4 different manufacturers and only about 15 were ever built IIRC.  Try looking for one on www.controller.com for one and you'll see that the brand isn't even listed because they've never sold one used.
If you want a long range single pilot jet, the best game in town is the Citation S/II with the Williams Engine FJ-44 engine mods by Sierra (called the Super S/II) or similar modder.  They can hold ~5800lbs of fuel and with the new engines, they climb faster, cruise faster, and burn less fuel.  They can go 2300-2600nm, depending on the upgrades.  This is basically the same airframe as the Citation 1 & Mustang (500/501 airframe) and Citation II & Bravo (550 airframe, longer than 500), but with more fuel capacity and a very efficient supercritical wing.
The Citation Super S/II (Sierra's modded plane) has a maximum takeoff weight of 15000lbs, so it has stricter standards to meet than a "Part 23" aircraft which must be under 12500lbs.  There is no jet that you can actually buy that weighs under 125000bs and can go 2600nm that I'm aware of, and believe me I have looked.  That makes the Super S/II the closest thing I've found to an affordable single-pilot jet for long missions.

Cessna Citation 501sp Eagle II, spx. has a 1,987 NM range.


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What is a trowal?
I'm trying to learn and understand the symbols on the significant weather charts and I found a symbol for "trowal". But I have no idea what trowal means. Can anybody explain what it is and how it's relevant to aviation?

(Source: Wikipedia)

What's wrong with the explanation at https://en.wikipedia.org/wiki/Occluded_front ?

I'm voting to close this question as off-topic because it better belongs on EarthScience.SE

There is a very complete education for TROWAL identification from Virtual Institute for Satellite Integration Training (VISIT).

I have never heard of a trowal, but if it is on weather map used for aviation I am interested. What is it? Why is important enough to be on the significant weather map. Does a trowal affect aviation? If not, why is it on the map? If it does affect aviation,  why is it off-topic?

@DeltaLima: A trowal is a thin occlusion of warm air ahead of a cold front meeting cool air. In that small warm atmospheric valley the aft cold front and the warm front ahead are very close. Further ahead of the trowal there is a high risk of icing, due to rain falling from the trowal thru a mass of cool air. Behind the trowal there is a risk of thunderstorm. Trowals seem to be more frequent  over Canada.

@mins thank you. So the trowal is basically the line where the three air masses of an occluded front meet. It is up in the air and, when projected on the map has a different location as the occluded front. A cold occluded frontline on the surface would be ahead of the trowal while a warm occluded frontline is trailing the trowal.

As a retired Environment Canada meteorologist I used trowal symbols on surface map analyses. The theory of how a trowal was formed was never proven, but a few decades ago a detailed upper air analysis of the air masses surrounding an occluding frontal system/low showed no warm air aloft where the trowal was supposed to exist. Apparently, the occlusion process mixed the cold and warm air masses leaving no detectable original warm air signal around the low.
The trowal was purely a Canadian feature on surface weather maps because it was thought that the more traditional occluded front represented only a weak temperature discontinuity that did not fit the associated weather pattern too well. Some analyses showed trowals extending from the decaying frontal vertex for hundreds of miles when no temperature contrast existed at the surface where an occluded front was supposed to be.
More research into the upper air features around occluding systems should eventually lead to new symbols replacing both the occluded front and trowal to better represent the physics for the sharp discontinuities and weather observed on satellite pictures, radars, and predicted by numerical models. The weather around these frontal lows is a lot more complex than can be represented by simplistic occluded fronts and trowals. I've noticed lately that Environment Canada's surface analyses have been dropping the use of trowals.


text:
Are landings easier during the day or at night?
When is it easier for a pilot to perform a "good" touchdown: during daytime or nighttime?
Considering typical flights for 737s to holiday destinations so mostly small airports with a single runway.
In the above, "good" is defined as a firm landing with both rear wheels simultaneously on the ground.
During the night the runway is brightly lit and all the guiding lights are clearly visible, but the actual tarmac is more difficult to spot. During the day there is flare from the sun and the lights are less visible but on the other hand the tarmac is clearly visible.

Newbie pilots train during the day at first, and night flying/landing is a later topic.  That alone says daytime is easier.

I'm going to answer this in somewhat of a more general sense but first let's clear up a few things.

During the night the runway is brightly lit and all the guiding lights
  are clearly visible, but the actual tarmac is more difficult to spot.

This is not always the case. Maybe at large international airports the runway is quite well lit with lots of extra lights, but there are plenty of airports in the US that are poorly lit (granted not all of them service commercial traffic); it's worth noting that not all runways are well lit. Runway lighting varies quite a bit as well.

During the day there is flare from the sun

Only if the sun is right in front of you, there are lots of runway directions and you may often land with the sun behind you.

...and the lights are less visible but on the other hand the tarmac is clearly visible.

The lights are not visible at all, they are off, but yes the tarmac is easy to see during the day.

A "good" landing by a proficient pilot should not be greatly affected by day or night conditions. What will affect a landing is the prevailing wind and weather conditions. Generally speaking wind (and thermal activity) dies down at night so the air is far more calm. In my experience night landings are smoother because of this. During a hot summer day, even in super clear weather, with the wind whipping and the clouds kicking thermals around you are bound to have a "fun" approach.
(from the FAA's handbook on night operations)

Night approaches and landings do have some advantages over daytime
  approaches, as the air is generally smoother and the disruptive
  effects of turbulence and excessive crosswinds are often absent

More recently LED light technology has allowed some extremely bright landing lights to be installed on even the smallest of aircraft, this has greatly increased pilot visibility on short final at night.

Thus with recent development in the lightning technology it is in general easier to land during nighttime given that it is; more quiet in the air and the air itself is calmer ?

Depth perception is always better in daylight.  You can see the entire surface and surroundings, not just a little spotlit patch ahead of you, which fades to black, then with bright lights in your peripheral vision.  Landing at night is a little bit like landing with tunnel vision.

I wouldn’t say one is easier than the other.  Obviously for nighttime, the runway needs to be illuminated or pilot controlled lighting available to properly spot and line up with the runway as well as for depth perception needed for the round-out (flare).
What is not readily available is the additional depth perception offered by daylight flying as well as terrain and obstacle identification and avoidance that is offere during daylight operations.  There have been plenty of accidents which have happened where a pilot has become accustomed to flying shallow approaches into an airport, then attempting to do so at night and struck terrain, buildings, sailboat masts, wires, etc because they were hidden in the darkness.  It’s often recommended that you fly a little higher approach at night into an unknown or previously unvisited airfield at night and thoroughly review the chart supplements for the airport in question as part of your preflight.
Optical illusions are also more prevalent at night than day.  Airfields with runways on an incline or sloping gradient will not be readily recognizable at night.  Also runways which are narrow present hazards during roundout, particularly if the pilot is used to landing on wide runways which may make him misjudge his height above the runway during round out.  Runway condition is another critical factor and it may be unadvisable to land on a runway which is not paved or is known to be soft or uneven.  Runway incursion by vehicles, people or animals is another hazard which also should be anticipated prior to flight.  Again the A/FD should be consulted and the width, layout and condition of the runway should be verified and anticipated as part of a preflight.
Often the most difficult thing about night ops is during arrival into the terminal area around the airport.  It’s often very difficult to spot an airport, particularly in big cities and urban environments from the ground clutter and nearby city lights.  Roads, rectangular, lighted parking lots, etc can often be mistaken for runways and it can be misleading.  Often times the intensity of the runway lighting is less than that of the surrounding buildings and roads and most pilots will intitially visually acquire an airport from the flash of the rotating beacon light.  It can also be especially difficult in a city like Wichita, KS with multiple airports clustered together or make use of runways aligned in the same direction.  Again it’s helpful to study a sectional chart to see where the airport is located in a particular city, the direction you anticipate arriving at said airport in order to determine how you will maneuver to set up in the pattern.  Often knowing the general area of a city where the airport should be will help you locate the rotating beacon in the ground clutter.
As for actually executing a landing at night on a properly lit runway, the actual act is not that different from doing it during daytime.  It also has some additional benefits in that the airspace and traffic around the airport is usually less congested that during daytime operations and the air is usually smoother at night than during the day.  But the limitations on visibility, peripheral field of view and darkness add in new considerations that a pilot needs to account for.

I upvoted your answer, I very much agree with your very first sentence. One caveat, though, "...depth perception needed for the round-out." While more often true than not, there are techniques that don't use depth perception for the round-out. Glassy water landings in seaplanes come to mind. You really can't accurately judge your height above glassy water. Also, you don't need depth perception when using a radar altimeter and landing by-the-numbers so to speak. See http://talking-of-flying.com#landing747 for an example.

Might be helpful to describe what is "roundout"?


text:
How to tell the difference between METAR and SPECI reports?
I am trying to use METAR data from AviationWeather.gov to programmatically collect hourly rainfall data.  This Wiki says that the first field in the report should be "type" - either METAR or SPECI.  METARs are sent every hour, SPECIs are sent sporadically under certain conditions.  The problem is that the AviationWeather.gov reports are missing that first field, so I can't tell the difference between METAR and SPECI reports.  I care because I can only get reliable cumulative Rainfall data from the METAR reports.
What am I missing?

Are you scraping data from the AWS METAR page, or parsing it from their data server feed? Assuming you're using the data server, the AWS format is documented here. But I'm not totally sure what you're doing.

I'm pulling it from the data server feed.  I'm looking at field 23 in the document you referred to.

Unless I missed something, field 29 is METAR/SPECI?

I don't think you can use METARs to produce precise hourly rainfall data. METARs do not express the exact amount of precipitation; rain is only expressed in three categories (light, moderate, heavy).
The way I understand your problem, you want to skip SPECI reports because you only want a single report per hour. A better way of doing this would be to use the time/date stamp in the report and simply dismiss a report if you already have one from the same hour. Say you have a report from 011203Z and you then receive another report from 011220Z. You want to dismiss the last report, because it is only 17 minutes older than the first one.
Alternatively, you can find METARs from a number of other sources, which include the message designator as well. Here is one I find useful: http://www.ogimet.com/metars.phtml.en

If I understand this document correctly, The data I want is: field 23, precip_in = Liquid precipitation since the last regular METAR

The problem with trying to detect the reports coming in every hour as you suggest, is that its so fuzzy.  For example, if I reports at the following times, which are METAR and which are SPECI?
1:00, 1:05, 1:40, 1:59, 2:00, 2:05, 2:40.
looking at KATL for example, you can see that most reports come in at 53 after the hour, so those are probably METAR, but its hard to code for that.

yes, http://www.ogimet.com/metars.phtml.en does specify METAR/SPECI, maybe thats the way to go


text:
How does an energy variometer work?
In a comment to an answer regarding instrumentation complexity, an "energy variometer" was mentioned, labeled in knots. What does this dial actually show, and how does it work?
The image accompanying the answer in the linked comment was this, with the energy variometer shown at the top left. Don't get distracted by the legs. :)

As it is labeled with +- knots, I would assume it is showing rate of change in airspeed (i.e. acceleration), but calling it an "energy variometer" suggests that it is a combination of altitude and airspeed in which case it would show positive when entering updrafts (or when being towed) which is obviously useful for a glider. Either way it would be interesting to know how it works.

When towed or when in a raising air (thermal or deflected by terrain), the later being point of having the instrument. I don't know how it works.

Oh right, of course, how dumb am I? Thanks, I'm editing that in.

you could have cropped the legs out (and copied the copyright) if you didn't want them to be distracting

The left instrument is an electronic version of the mechanical one (right side, works without battery). The electronic vario has an additional acoustic signal which indicates climb speed, so the pilot must not stare at the instruments all the time.

The energy variometer gives the rate change of total energy of the aircraft expressed in vertical knots.
A traditional variometer gives the vertical speed of the aircraft derived from the change in barometric pressure. This is very useful for gliding, especially when looking for thermals that lift you up. The problem with ordinary variometers is that they do not indicate why the glider is climbing; is it due to a thermal / ridge wind or is it because the pilot pulled up and the aircraft is losing speed.
When the aircraft is climbing in a thermal or ridge wind, the total energy is increasing. When the aircraft is climbing while it is exchanging speed for altitude the total energy is constant (neglecting drag).

Energy equations
Total energy is the sum of kinetic energy and potential energy:
$E_{tot} = E_{kin} + E_{pot}$
Kinetic energy is proportional to the velocity squared:
$E_{kin} = \tfrac{1}{2}mV^2 $
Potential energy is proportional to the height:
$E_{pot} = mgh$
So a change in total energy is the result of the changes in kinetic and potential energy.
$\Delta E_{tot} =\Delta  E_{kin} +\Delta  E_{pot}= \tfrac{1}{2}m\Delta(V^2)+mg\Delta h$
Differentiating with respect to time gives:
$\frac{\textrm{d}E_{tot}}{\textrm{d}t} =mV\frac{\textrm{d}V}{\textrm{d}t}+mg\frac{\textrm{d}h}{\textrm{d}t}$
The climbrate ($\frac{\textrm{d}h}{\textrm{d}t}$) resulting from exchange of kinetic energy to potential energy can be expressed by:
$\frac{\textrm{d}h}{\textrm{d}t} = -\frac{V}{g}\frac{\textrm{d}V}{\textrm{d}t}$
with $-\frac{\textrm{d}V}{\textrm{d}t}$ being the deceleration.
This is the correction that is applied to the ordinary variometer to obtain the energy variometer. This can be done in an electronic way but amazingly it can also be done by mechanical pressure measurement.

Total energy and pressure measurements
When we look at pressure measurements that are used to calculate the airspeed, there is a striking similarity to the energy equation.
A pitot tube facing the incoming airflow measures total pressure which is the sum of static pressure $P_s$ and the dynamic pressure $q_c$
The dynamics pressure, which is the measure for airspeed, is given by
$P_t =P_s+q_c =P_s + \tfrac{1}{2}\rho V^2 $
Note that $q_c$ scales proportionally with kinetic energy. The static pressure changes with height but it decrease while potential energy increases.
When mounting the pitot tube backwards with the total pressure port facing backwards, the total pressure measurement would change to:
$P_t =P_s-q_c =P_s - \tfrac{1}{2}\rho V^2 $
When the aircraft trades kinetic energy for height, the speed drops so the term
$-\tfrac{1}{2}\rho V^2$ would increase in value (becomes less negative).
At the same time, the static pressure $P_s$ decreases with the same amount due to the climb. The result is that the total pressure measurement from this aft facing port remains unchanged when the total energy of the aircraft is constant. That is why an aft facing pitot port is called a Total Energy probe (TE probe).
The rate of change of the $P_t$ is a direct measure of the rate of change of total energy. So while an ordinary variometer measures rate of change of static pressure, the energy variometer measures rate of change of the total pressure of an aft facing pitot port.

To work best, a TE probe must be in undisturbed air. This is difficult as the probe itself is ahead of the pressure port so there is always some turbulence affecting the measurement. A common approach is to have the probe stick out in front the vertical stabilizer.

The pressure port is at the end of the tube, facing the vertical tail plane:

More than showing why you're climbing, it could show positive even when descending (accelerating in a descent faster than just trading altitude for airspeed), making it easy to determine if you're entering an updraft. Very cool indeed, thanks for the answer!

I thought that all variometers use energy compensation since maybe 50 years. The picture shows two because one is an electronic version (left side) of the mechanical one (right side, works without battery). The electronic vario has an additional acoustic signal which indicates climb speed, so the pilot must not stare at the instruments all the time.

Plenty of gliders have uncompensated varios. And if you read the answer carefully, it doesn't show or sound climb speed, but change in total energy.

A variometer is a similar instrument to as a VSI (Vertical Speed Indicator) or VVI (vertical velocity indicator).
They are very important in gliders (what it appears the picture shows), as it indicates the presence of rising or sinking air. In powered flight, they are used to indicate level flight (or set a desired descent rate).
Gliders utilize a calibrated variometers (the aforementioned energy variometers), as an uncalibrated variometer will combine the aircraft's sink rate or rise with the sink rate or rise of the airmass.
As far as how it works,

In most sailplanes, total energy compensation is achieved by connecting the variometer to the atmosphere via a "total energy probe", that produces vacuum proportional to the square of the glider's air speed—in effect, a negative pitot. Alternatively, the subtraction may be done electronically by the flight computer based on indicated airspeed (pitot).

This article gives a more detailed explanation, especially as it relates to changes in energy:

A TE variometer doesn't indicate vertical speed. It shows the rate-of-change of the glider's total energy per unit of weight - therefore it's name.
  It measures the variation of the glider's total energy, which is the sum of
  potential energy (proportional to altitude) and kinetic energy (proportional
  to the square of velocity). Its indication can only be regarded as being equal to true vertical speed in the case where kinetic energy does not change, in other words: where the absolute value of velocity (airspeed) remains
  constant. In contrast, a non-compensated vario will measure the rate of change of potential energy alone, which means the rate of change of altitude, or true vertical speed, independent of whether the glider's velocity changes or not. Conclusion: the two
  types of variometers indicate the same
  only when the glider's airspeed does not
  change.

If you are looking for an exact formula, this article shows how to calculate the relation between total energy and pressure.
TL; DR: The total energy variometer indicates the presence of thermals or other changes in total energy by removing energy 'trades' from the picture (e.g. airspeed for altitude), that would display differently on a normal VSI.

Energy variometer is not a "more precise" variometer, it measures a fundamentally different quantity (or specific quantity if you take "variometer" to mean any instrument indicating differential). Note, that the image above has energy variometer on the left and vertical speed indicator on the right.

@JanHudec - ahh, thanks for that clarification


text:
Upgrading a Sport license to a Private license - is a new student license necessary to solo non-LSA aircraft?
I hold a sport pilot certificate and a valid third class medical. I'm pursuing a private pilot certificate and receiving training in C172's and C182's, though I also have access to a C162. I was wondering if I can be signed off to solo in the non-LSA aircraft without going through the process of obtaining a student pilot certificate, and just getting the logbook endorsement as follows:

I certify that (First name, MI, Last name) has received the required presolo training in a (make and model aircraft). I have determined he/she has demonstrated the proficiency of FAR 61.87(d) and is proficient to make solo flights in (make and model aircraft).
  4/25/14 J. J. Jones 987654321CFI Exp. 12/31/05

I have several solo missions that could benefit from additional power and useful load provided by the larger aircraft, but with the new student pilot certification process, I'm wondering if it's worth the hassle.

I don't have time to research and verify, but I believe once you have a pilot certificate, you no longer qualify for a student certificate.  If I'm not mistaken, you may forego the signature required on the reverse of the student license and just receive the logbook endorsement.

You do not need to get another student pilot certificate.  The endorsement you need is not for student pilots.

A.72 To act as pilot in command of an aircraft in solo operations when the pilot does not
hold an appropriate category/class rating: § 61.31(d)(2).

I certify that [First name, MI, Last name] has received the training as required by
§ 61.31(d)(2) to serve as a pilot in command in a [specific category and class] of aircraft.
I have determined that [he or she] is prepared to solo that [make and model] aircraft.
Limitations: [optional].

The answer lies in Advisory Circular 61-65. Version H, issued August 27, 2018, is the latest as of May 2023.

Does this endorsement have the 90-day expiration of the student solo endorsement?

No.  There is no time limitation listed in the FARs... however, the instructor would be wise to place one on the endorsement.


text:
What do "LC/P" and "PTD" stand for in reference to airport communications?
When I pull up the Colorado Springs (KCOS) Airport Comm frequencies in Skyvector or in FAA database there are some frequency listed as "LC/P" and "PTD". Would someone explain what those acronyms stand for?

LC/P: 119.9 360.6
  PTD:    122.85 372.2

PTD means "Pilot to Dispatcher" according to the Airport / Facility Directory Legend.

LC/P: Local control, primary frequency, from LC, local control, which is a usual control position in the tower.

"The Local Controller is primarily responsible for separating and providing safety alerts to aircraft in the airspace surrounding the airport and aircraft on the active runways" (source)

Source

PTD: As @Riccati commented, it means Pilot to Dispatcher, according to the Airport / Facility Directory Legend.

Airlines are required by regulation to provide direct communication means for aircrew.

Aircraft dispatcher training (source)

See also: Can airline pilots communicate with dispatchers?


text:
Can I maintain my IR currency from the right seat in a non "N" registered aircraft?
I completed my IFR checkride on the 15th of May this year, the next day I moved to Spain to study my EASA ATPL (airline transport pilot license).
A friend of mine here in Spain is doing his time building and I am allowed to sit in the right seat with him. Would I be allowed to log my approaches (66HIT) from the right seat even though I don't have an EASA PPL and the aircraft is registered in Spain?
I ask because that would save me the cost of paying for an instructor and a checkout flight as well as the hassle of flying alone in airspace which is completely new to me!

Related:  https://aviation.stackexchange.com/questions/154/can-time-logged-in-foreign-aircraft-be-applied-towards-an-faa-certificate-or-rat

In my opinion, no.
§61.51(g) states that one must log instrument time to meet the instrument experience requirements of §61.57(c), and defines instrument time as "that flight time when the person operates the aircraft solely by reference to instruments under actual or simulated instrument flight conditions."
§1.1 defines flight time as "Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing."
All of the types of "pilot time" that can be logged are described in §61.51. Since you are not rated to act as PIC or SIC, none of them apply to you (unless your friend is an authorized instructor, anyway).
Essentially, from a legal standpoint you are a passenger, not a pilot. Therefore your time in the plane is not "pilot time," and it follows that it is not "instrument time" either. So you cannot log anything to meet the currency requirements.

Non of what you quoted says anything about aircraft registration.

@MichaelHall The FAA only has the authority to authorize a pilot to act as PIC or SIC in US-registered civil aircraft or that is flown within the NAS. By implication, I don't see how OP can be considered to be rated in an aircraft of Spanish registry or acting as a pilot in one.

If EASA recognizes his FAA certification does that change the answer?

@MichaelHall Yes, I think so.